Shape-memory alloys (SMA) are strong-lightweight alloys that can be programmed to remember different shapes at different temperatures. SMAs, such as Nickel-Titanium (Ni—Ti), display two distinct crystal structures or phases. Martensite form exists at lower temperatures, and austenite form exists at higher temperatures. When an SMA is in martensite form at lower temperatures, it can be easily formed to a desired shape. When the SMA is in austenite form at higher temperatures, it can be “trained” to transition into another shape. For example, the SMA may be bent, squeezed, twisted, or otherwise formed to have a different shape when in the austenite form. The SMA when heated will transition from its low-temperature (martensite) shape to its high-temperature (austenite) shape. When heat is removed and the SMA cools, the SMA may be trained to transition back from its high-temperature shape to its low-temperature shape.
SMAs have applications in many different areas, such as aircraft and aerospace. Manufacturers continue to look for improved ways of using SMAs.